1. Scope

ASTM International Committee D19 on Water is working to develop analysis methods and practices that will standardize the collection, sample preparation, and analysis of microplastics in water and wastewater. A major issue with the sampling of microplastics is their unique behavior; microplastics occur as non-homogeneously distributed particulates and fibers composed of various polymeric materials. Data has shown that the potential for sample cross-contamination during collection, preparation, and analysis shall be minimized. Count-based identification methods require rigorous preparation techniques when separating polymers from other organic and inorganic materials in water samples with high to low levels of suspended solids. This Py-GC/MS method enables users to achieve polymer identification and mass quantitation directly from the sample with minimal particle separation, and thus, it is potentially applicable to other sample matrices such as soils, sediments, biosolids, and air. Py-GC/MS is not constrained by lower particle size (for example, 10 to 20 um) limitations typical with IR and Raman count-based imaging identification methods. To reflect accurately the true polymer identification and quantity (mass) of particles and fibers in the sample, this standardized method for analysis needs to be established.
This analysis method is to be used in conjunction with other ASTM International microplastic standards, one of which is also in development.
Per Practice D2777, 1.7, the precision of this test method is based on the results of the single-operator (laboratory) validation study conducted in 2020. An approved plan for an interlaboratory study of this test method will be available to interested parties to be initiated thereafter and a complete precision statement is expected to be available within five years of approval and publication.

Keywords

all water matrices; analytical quality assurance; back-flush; calibration reference standard; calibration samples; cold-trap; collection procedures; continuing calibration check sample; count-based; cryo-trap; effluent; field duplicates; grinders; HDPE; high turbidity waters; influent; laboratory duplicates; LDPE; linear dynamic range; low turbidity waters; mass-based; microplastic; microplastic contamination; microplastic fibers; microplastic particles; microplastic pollution; microplastics; microplastics in drinking water; microplastics in wastewater; nanoparticle; nanoplastic particles; PE; PET; polymers; PP; pre-column; proficiency samples; PS; PVC; Py-GC/MS; pyrogram; pyrolysis; quality assurance; quality control; quantification procedures; quantitation; raw sewage; reactive pyrolysis; reference samples; retention indices; retention time; sample cup; sample preparation; sampling procedures; simulation samples; suspended solids

Rationale

Microplastics are now recognized as pervasive in the environment, including wastewater effluent, the ocean water column, sediments, animal tissue, and even drinking water. This pervasiveness has led to product bans for small plastics, such as microbeads used in cosmetic products, to larger plastic items that can degrade into microplastics, such as bags and straws. In addition, there are new and planned requirements to monitor microplastics in the environment, wastewater effluent, and in drinking water. Implementing monitoring programs requires reliable standardized methods and best practice guidelines. Such methods enable comparison of studies and the ability to compare quantification among sources. Although the quantification and characterization of microplastics in samples has been occurring for more than a decade, the results are not necessarily reliable or comparable because neither standard field and laboratory methods for collection and identification nor the reference materials necessary for quality assurance yet exist. At this time the State of California and partner agencies are about to begin formal studies and monitoring programs for microplastics in drinking water and wastewater, and development of this standard is vital to support their efforts and efficacy.

The title and scope are in draft form and are under development within this ASTM Committee.